On the standing wave mode of giant pulsations

Both odd-mode and even-mode standing wave structures have been proposed for giant pulsations. Unless a conclusion is drawn on the field-aligned mode structure, little progress can be made in understanding the excitation mechanism of giant pulsations. In order to determine the standing wave mode, we have made a systematic survey of magnetic field data from the AMPTE CCE spacecraft and from ground stations located near the geomagnetic foot point of CCE. We selected time intervals when CCE was close to the magnetic equator and also magnetically close to Syowa and stations in Iceland, and when either transverse or compressional Pc 4 waves were observed at CCE. Magnetograms from the ground stations were then examined to determine if there was a giant pulsation in a given time interval. One giant pulsation was associated with a compressional wave, while no giant pulsation was observed in association with transverse wave events. The CCE magnetic field record for the giant pulsation exhibited a remarkable similarity to a giant pulsation observed from the ATS 6 geostationary satellite near the magnetic equator (Hillebrand et al., 1982). In agreement with Hillebrand et al., we conclude that the compressional nature of the giant pulsation is due to an odd-mode standing wave structure. This conclusion places a strong constraint on the generation mechanism of giant pulsations. In particular, if giant pulsations are excited through the drift bounce resonance of ions with standing Alfvén waves, ω - mωd = ±Nωb, where ω is the wave frequency, m is the azimuthal wave number, ωd is the ion drift frequency,N is an integer, and ωb is the ion bounce frequency, then the resonance must occur at an even N

Stellar X-rays and magnetic activity in 3D MHD coronal models

Observations suggest a power-law relation between the coronal emission in X-rays, $L_{\rm{X}}$, and the total (unsigned) magnetic flux at the stellar surface, $\Phi$. The physics basis for this relation is poorly understood. We use three-dimensional (3D) magnetohydrodynamics (MHD) numerical models of the coronae above active regions, that is, strong concentrations of magnetic field, to investigate the $L_{\rm{X}}$ versus $\Phi$ relation and illustrate this relation with an analytical model based on simple well-established scaling relations. In the 3D MHD model horizontal (convective) motions near the surface induce currents in the coronal magnetic field that are dissipated and heat the plasma. This self-consistently creates a corona with a temperature of 1 MK. We run a series of models that differ in terms of the (unsigned) magnetic flux at the surface by changing the (peak) magnetic field strength while keeping all other parameters fixed. In the 3D MHD models we find that the energy input into the corona, characterized by either the Poynting flux or the total volumetric heating, scales roughly quadratically with the unsigned surface flux $\Phi$. This is expected from heating through field-line braiding. Our central result is the nonlinear scaling of the X-ray emission as $L_{\rm{X}}\propto \Phi^{3.44}$. This scaling is slightly steeper than found in recent observations that give power-law indices of up to only 2 or 3. Assuming that on a real star, not only the peak magnetic field strength in the active regions changes but also their number (or surface filling factor), our results are consistent with observations. Our model provides indications of what causes the steep increase in X-ray luminosity by four orders of magnitude from solar-type activity to fast rotating active stars.Comment: Updated version after review: 15 pages, 12 figures, Accepted for publication in Astronomy and Astrophysic

Рекомендации по ограничению динамических перенапряжений в обмотке ротора асинхронизированного турбогенератора

In this paper, a Volume-of-Fluid (VOF)-based approach for the Direct Numerical Simulation (DNS) of reactive mass transfer in gas–liquid flows is described. At the interface, local thermodynamic equilibrium is assumed and modelled by Henry's law. First numerical simulation results are presented for non-reactive and reactive mass transfer from rising gas bubbles to a surrounding liquid. For the evaluation of reactive mass transfer simulations with a consecutive, competitive reaction system in the liquid, a local selectivity is employed

GroEL dependency affects codon usage—support for a critical role of misfolding in gene evolution

Integrating genome-scale sequence, expression, structural and protein interaction data from E. coli we establish an interaction between chaperone (GroEL) dependency and optimal codon usage.Highly expressed sporadic substrates of GroEL employ more optimal codons than expected, show enrichment for optimal codons at structurally sensitive sites and greater conservation of codon optimality under conditions of relaxed purifying selection.We suggest that highly expressed genes cannot routinely utilize GroEL for error control so that codon usage has evolved to provide complementary error limitation, whereas obligate GroEL substrates experience relaxed selection on codon usage.Our results support a critical role of misfolding prevention in gene evolution

INVESTIGATION OF THE MECHANISMS OF HEAT EXCHANGER CORROSION IN A MUNICIPAL WASTE INCINERATION PLANT BY ANALYSIS OF THE RAW GAS AND VARIATION OF OPERATING PARAMETERS

The detailed mechanism of high temperature chlorine corrosion, the dominant cause of corrosion in a municipal solid waste incinerator (MSI), has still to be clarified (Schroer, 2002). Upon its way through the boiler the raw gas is subject to various physical and chemical processes and interactions. Of these, sulphation of chlorides is supposed to have the major impact on chlorine corrosion (Neumann, 1997). The physical and chemical mechanisms of corrosion were investigated at a municipal solid waste incinerator. Both, the particulate and gas phase of the flue gas, were chemically and physically analyzed during their way through the boiler, at temperatures from close to 1000 °C down to 200 °C. The raw gas composition was analyzed during normal operation and soot blowing cleaning routine. Additionally, operating parameters of the plant were varied, and deposition processes were evaluated with the aim to find out primary measures to reduce corrosion rates. The particle mass concentration exhibits a bimodal size distribution with maxima at approximately 0.5 μm – growing by duration of travel – and 100 μm. First results show that sulphation of the particles can be observed upon travel through the boiler and on the fouling. Sulphur containing additives increased the sulphation of the particles during flight though not to completion

Social Support Needs of Minority Breast Cancer Patients: Significance of Racial Homogeneity and Kin Composition of Social Networks

Social support from family and friends assists breast cancer patients navigate a life crisis, but more needs to be understood about specific social network characteristics that can benefit breast cancer patients. To address this need, the primary aim of this study was to identify social network factors that facilitate or reduce social support. Given racially patterned gaps in social support among breast cancer patients, a secondary goal was to identify network characteristics that are linked to gaps in support. We examined these research questions using data from a sample of 915 breast cancer patients (NHWhite=373; NHBlack=377; Hispanic=165) and 4,021 of their network members. To improve on prior research, we collected detailed social network data using a personal-network measurement tool and assessed needed and received support on five support components. Study findings identified specific network characteristics that facilitate these social support components. Network size was associated with increased practical, informational, emotional, and spiritual support. Network density was associated with increased practical support. Racial homogeneity in networks were associated with reduced informational support while a higher number of daughters in support networks was associated with increased emotional support. Compared to NHWhite patients, NHBlack patients were more likely to experience inadequate practical and financial support. Additionally, compared to NHWhite patients, Hispanic patients were more likely to experience inadequate informational and emotional support. The study found that network density, racial homogeneity, and gender composition of NHWhite, NHBlack and Hispanic social networks contributed to the racially patterned disparities in social support. Findings in this study could inform interventions aimed at increasing social support through greater mobilization of existing network ties as well as policy-driven, formal community building initiatives aimed at replicating benefits of naturally occurring networks

Исследование спектральных свойств когерентного дифракционного излучения от периодических структур

При пролете электрона вблизи периодической структуры генерируется поляризационное излучение, называемое дифракционным излучением от периодических структур (grating diffraction radiation). При пролете электрона параллельно решетке возникает хорошо изученное излучение Смита-Парселла. Однако при непараллельном пролёте также может возникать излучение. В данной работе проводится анализ спектральных характеристик когерентного дифракционного излучения от решеток, экспериментально полученных на ускорителе KEK-LUCX (г. Цукуба, Япония). Представлены спектры излучения, получаемые при разных углах ориентации решетки. Полученные спектральные характеристики сравниваются с теоретически рассчитанными.When an electron passes close to the periodic structure polarization radiation is generated, called diffraction radiation from periodic structures (grating diffraction radiation). When an electron passes parallel to the grating, well-studied Smith-Purcell radiation arises. However, in the case of a nonparallel flight, radiation can also occur. In this work, we analyze the spectral characteristics of coherent diffraction radiation from gratings, experimentally obtained at the accelerator KEK-LUCX (Tsukuba, Japan). Radiation spectrums obtained at different angles of grating orientation are presented. The obtained spectral characteristics are compared with theoretically calculated

Characterisation of a Coriolis flow meter for fuel consumption measurements in realistic drive cycle tests

When testing light-duty and heavy-duty vehicles on chassis dynamometers, as in the WLTP, or engines on engine test benches, as in the WHDC, it is required to measure the fuel consumption. In the preferable case, the measurement of the fuel consumption is carried out with suitable flow meters. These require high measurement accuracy in a wide flow range, independent of the fuel type, as the flow rate range is often very large and depends on the power range of the vehicle engines. Moreover, the fuel flow rate in the test cycles is very dynamically related to the loads. In the scope of the ongoing EMPIR Joint Research Project 20IND13 SAFEST the dynamic flow behaviour as well as the measurement accuracy of flow meters for different types of fuels are investigated. This paper presents first results from the realisation of dynamic flow profiles, and flow measurements with a Coriolis Flow Meter with different representative fuels in a wide density and viscosity range and a wide flow rate range at different fuel temperatures